Question

a ball is thrown vertically upward with a speed of 25m/s, a) how high does it rise. B) how long does it take to reach its highest point? C) how lnong does the ball take to hit the ground after it reachest highest point? D) what is the velocity when its returned to the level from which it started?

Answer 1

V= U+at
where
a ball is thrown vertically upward with a speed of 25m/s, a) how high does it rise. B) how long does it take to reach its highest point? C) how lnong does the ball take to hit the ground after it reachest highest point? D) what is the velocity when its returned to the level from which it started?
V ( the final velocity at the highest point)= 0 m/s ( the spped of the object reduces to zero when it reaches the highest point)

u ( the initial velocity) = 25.2 m/s
a= - 9.8 m/s^2 ( negative sign since the boby id moving against gravity)

substituting these valuse in the above equation we get

0 = 25.2 - 9.8 * t
t = ( 0 - 25.2 ) / ( - 9.8)
= 2.75 seconds

now to find how high it rises ,use the equation
S = Ut + (a* t * t )/2
= 25.2 * 2.57+ ( - 9.8 * 2.57 * 2.57 ) / 2
= 32.4 meters

time taken to reach the highest point = 2.57 seconds
time taken for the ball to hit the ground after it reaches its highest point = 2.57 seconds

the velocity when it returns to the level from which it started is the same 25.2 m/s
to get this answer just know that the ball is at a height of 32.4 meters,now its initial speed is zero and it is falling under gravity a= 9.8 m/ s^2